Ocean-atmosphere coupling effects on the precipitation climatology over the eastern Adriatic and Dinaric Alps

Regional climate models incorporate multiple components of the climate system to address the need for more reliable information at regional scales, resulting in the regional climate system models (RCSMs). These models are particularly important for regions like the Mediterranean, where complex interactions and feedback processes among different climate components, especially the atmosphere and ocean, significantly impact local climate. In the Adriatic region, for example, air-sea interactions play a critical role during autumn, when strong temperature gradients between the sea surface and the atmosphere are most pronounced. High-frequency coupling resolves these rapid air-sea feedbacks and moisture transport from sea to land, thereby enhancing the extreme precipitation representation. However, uncertainties remain, particularly regarding the impact of coupling over inland areas far from the coupling areas themselves. Furthermore, the coupling effects vary by region and season, highlighting the need for further investigation.

To assess these impacts at the climatological scale over the eastern Adriatic and Dinaric Alps, we compare daily precipitation from the atmospheric regional climate model CNRM-ALADIN64 and the fully-coupled CNRM-RCSM6, which includes the atmosphere, aerosols, land surface, ocean and river components of the Mediterranean climate. Both models share an identical atmospheric component to isolate the coupling effects as accurately as possible. The precipitation analysis system MESCAN-SURFEX is used as a reference dataset and a range of basic climatological and extreme precipitation indices is analysed for the 1980 to 2018 period (39 years).

Our results show that the coupling has a modest overall effect. The strongest effect is reported during summer months, when it enhances precipitation frequency and intensity of both mean and extreme precipitation, resulting in better agreement with observations.  Although the long-term impact of coupling is relatively subtle, our findings suggest that incorporating sub-daily sea surface temperature variations could further enhance the accuracy of specific heavy precipitation events.